1. Field of the Invention
The invention relates to a polarizing optical arrangement, and more particularly to an optical arrangement that generates linearly polarized beam clusters before splitting the beams by a splitter grating to generate phase-displaced signals which form a rotary field without generating a constant light signal.
2. Description of the Prior Art
Various length and angle measuring instruments use polarizing optical arrangements. Foe example, U.S. Pat. No. 5,035,507 (Nishioki et al.) corresponding to German Published, Non-Examined Patent Application 39 42 385, describes a length measuring arrangement in which measurement signals are generated by means of refraction gratings, polarizers, beam splitters, a quarter-wavelength plate, analyzers, and optical detectors. The measured signals have a phase displacement of 45.degree. from a reference signal. The reference signal is a constant light signal furnished by detector 22A. The constant light signal does not interfere with the other partial beam clusters thus interference bands are created.
In an optical arrangement according to the Nishioki et al. patent, the relative phase position of the interfering partial beam clusters is fixedly determined by the physical construction of the arrangement. Therefore after the splitter grating the partial beam clusters are created by means of analyzers 28B and 28C, a quarter-wavelength plate and detectors which generate signals that are phase-displaced 90.degree. from one another. By reason of the physical construction of the arrangement, no other phase relationship is possible.
An object of the present invention is to create a polarizing optical arrangement in an interferometric measuring instrument having interfering partial beam clusters of the most equal possible modulation and intensity can be generated by being split open at a grating.
Another object of the present invention is the simple evaluation of identical types of signals, a so-called rotary field, for instance, three signals phase-shifted from one another by 120.degree..